Advanced Materials Research Vols. 594-597

Abstract: Reservoir water level is one important factor influencing the stability of landslides. The dynamic response of landslide stability under reservoir water level function and its features are analyzed using theoretical and numerical methods. The results show that, in terms of reservoir water level fluctuation and landslide permeability, the seepage filed of landslide can be divided into four types: lag behind impoundment(X-Ⅰ), lag behind drawdown(T-Ⅰ), synchronization with impoundment(X-Ⅱ) and synchronization with drawdown (T-Ⅱ). Under lag behind drawdown, at a certain rate of reservoir drawdown, the stability drops with the permeability of landslide. Under lag behind impoundment, with the rise of water level, the lower the permeability of landslide is, the more stable the landslide is. Under synchronization with impoundment or drawdown, the stability of landslide drops with reservoir impoundment and rises with reservoir drawdown.

Abstract: Dayantang slope was stable before Shuibuya project construction. Based on the long-term safety monitoring, it has appeared the obvious deformation during the project construction. According the monitoring datas, the stability of the landslide before and after the construction was discussed and analyzed. Considering the rainfall effect on landslide after it has been strongly anthropogenic disturbance, the numerical results show that it is in critical steady state without rainfall, while get worse and even unstable failure under the influence of the intensive rain and the long period of rainfall.

Abstract: In this paper, the effects of the main property indexes on the saturation original loess liquefaction is analyzed through the dynamic triaxial test by using the WF-12440 testing system, combined with the experimental results, the influence of density-grain degree coupling on saturated loess liquefaction is comprehensively analyzed. The result shows that the influence of density-grain degree coupling on saturation loess liquefaction has a feature of segmentation, plastic index plays the main role for loose loess, whereas density is the main control factor to dense loess; Moreover, the influence of density-grain degree coupling on saturated loess liquefaction controlled by cyclic numbers of the vibration, plastic index plays the leading role while the vibration times is small, while the more vibration times, the bigger density and higher strength of liquefaction.

Abstract: Generally the shear strength of saturated soils has been predicted by the Mohr-Coulomb theory. However, field data accumulated in the past have evidently shown that saturated conditions are actually never reached in arid and semi-arid regions. An analytical model is developed to predict shear strength of an unsaturated soil with respect with matric suction. The formulation takes into account the influence of the mean stress on soil water retention curves. The results of the model developed for predicting the shear strength are compared with available experimental results. The good agreement between the estimates and the experimental data indicates that the proposed equation is promising and reliable for estimating preliminary unsaturated shear strength parameters.

Abstract: With two different distributions of matric suction, the unified solution of passive earth pressure for unsaturated soils is obtained, which is based on the unified shear strength for unsaturated soils in terms of two independent state stress variables and could avoid some shortages of Rankine's passive earth pressure. The influence of intermediate principal stress and matric suction on passive earth pressure is discussed. The results show that the passive earth pressure increases significantly with the unified strength theory parameter or matric suction increasing, and does not change more rapidly when matric suction decreases linearly with depths than that is constant.

Abstract: Residual soils are weathering products of rocks that are commonly found under unsaturated conditions. Residual soil is one of special soils, and its engineering geology property is usually different because of the difference of resource rock type, the geology environment and weathering condition. By the means of analysis of the data attained by the methods of field exploration, laboratory test and testing in-situ, the physical and mechanical properties of the residual diorite in Jinan were studied deeply. It is proved that the stratigraphic section of the soil can be classified as two layers on the perpendicular direction. Considering the inhomogeneity of the residual soil mass and the widely divergence of the value of mechanics properties, the suggestion value of c, Φ , a, Es, fak were put forward for further guiding the engineering practice , on the base of physics and mechanics properties tests and the region practice experience. At the same time, it is pointed out that, at that region, the interlayer and inhomogeneity of the weathering layers should be emphasized in the process of projecting and constructing when the residual diorite acts as the foundation of the construction or one of the geologic layers.

Abstract: The mechanical parameters of the rock masses are scale dependent because of the existence of the discontinuities. The self-similarity of the discontinuities makes the application of fractal theory in the description of the rock mass structure possible. The novel point in this study is that the structure representative elementary volume (SREV) of rock mass is proposed. Rock mass structures were obtained through the two-dimensional discontinuity network simulation results, from which ten pieces of square rock mass specimens were chosen. The side lengths of the specimens were increased in turn from 1m to 10m. And the fractal dimension of each specimen with different sizes was calculated by the box-counting principal of the fractal geometry. The fractal dimensions of the rack mass structures became larger with their side lengths increasing, and finally stable. And the SREV of the rock mass was determined based on the variation rule of the fractal dimensions. Further, the relation between the structure representative elementary volume (SREV) and mechanical parameter representative elementary volume (REV) was qualitatively analyzed from the strength differences between the discontinuities and intact rock. And the conclusion was inferred that the size of the SREV was the upper limit of mechanical parameter REV. Meanwhile, the conclusion was verified by the results of the finite element method. This study can provided a referring value for the estimation of the mechanical parameter REV in future.

Abstract: Considering the variation of the porosity and permeability of coal containing gas at differential deformation stages, a dynamic model for porosity and permeability is developed based on the previous researches. Furthermore, taking coal containing gas as a kind of isotropic elastoplastic material and taking into account the effect of gas adsorption, the stress and seepage equations are derived and, the solid gas coupling model for coal containing gas is constructed, which is appropriate to describe the skeleton deformability of coal containing gas and the compressibility of gas under the solid-gas interaction condition. In addition, the numerical simulation model is built by using the finite element method, and the numerical calculation solution of the model for a special loading case is given in term of the constraint conditions and corresponding parameters. The research results may have significance for further enriching and improving solid-gas coupling theories for coal containing gas.

Abstract: The existence of interlayers has great influence on the stability of salt cavern. Based on the research results of creep test and other mechanical properties of salt rock and interlayer in Yunying Salt Mine, Hubei Province, cylindrical singular calculation model of salt rock cavity is built, and the corresponding simulation is conducted. Hard interlayer’s constraint influence on the creep contraction deformation of salt cavity is demonstrated. In addition, how the number of interlayers affects cavity radial deformation is discussed too. The results are important to oil-gas storage cavern modeling analysis in laminated salt rock.

Abstract: The speed of development of well test technology has been faster than well test interpretation technology in low permeability reservoirs. One of the main research directions for well test soft technology was specific interpretation theory and interpretation techniques. In recent years, well test was put forward higher request by the production complex and low permeability reservoirs. Test interpretation results urgently need to be applied to reservoir engineering analysis in-depth and quantitatively. One of the limited reality conditions of well test application was lack of the comprehensive research combined with the reservoir engineering. Combining with the test examples, the investigation radius change between injection-production wells was studied, and the build-up well test cycle in low permeability reservoir was optimized. According to the actual process situation, it was proposed that take 20d as the upper limit of well test cycle, and 10d block as the lower limit of well test cycle of build-up well test in a typical low permeability reservoir.